The invention relates to the field of hydraulic power systems, where an actuator mechanism such as a piston or an hydraulic motor is operated by delivery of a fluid under pressure, typically an oil pressurized and delivered by a power source such as an electric motor pump.
A standard hydraulic power system comprises a reservoir, an electrically powered pump, a filter, a relief valve, an accumulator, a pressure regulator or cut-out valve or switch, and a check valve, all linked in fluid communication by suitable conduits. The reservoir contains a supply of liquid to be delivered by the pump, which is usually light mineral oil or castor-based oil, and also accommodates the returning liquid from the actuator mechanism. Such oils have a low freezing point and additionally serve as lubricants for the system. Specialty hydraulic oils possessing various desirable characteristics are well known in the industry. The pump is connected or formed as part of an electric motor and provides pressure to deliver the liquid as desired. Well known types of pumps include gear pumps or radial cylinder pumps. The filter is typically disposed in the suction line which draws oil from the reservoir either immediately before or after the pump and ensures the liquid remains free from foreign matter. The accumulator is a secondary storage chamber of variable volume which smooths out pressure fluctuations and ensures a steady build-up in addition to storing liquid under pressure for emergency or supplementary use. The cut-out valve automatically bypasses the actuator mechanism and delivers the high-pressure liquid back to the reservoir when a maximum pressure is reached. The check or non-return valve prevents liquid from leaking back when the cut-out valve is actuated. The relief valve is a redundant safety feature in the event the cut-out valve fails to operate properly. The hydraulic power system delivers the liquid under pressure to different actuator mechanisms, such as a selector valve, jack, piston, motor or other device which operates a particular piece of equipment or the like.
Conventional hydraulic systems, and especially those used to operate large equipment or other heavy duty mechanisms, suffer from numerous drawbacks. The systems are usually noisy and very energy inefficient, drawing excessive current and thereby increasing operating costs. The system components occupy a relatively large volume and footprint. As the pumps are usually operational only at full power, they are difficult to fine tune for precise load delivery and difficult to power down to deliver low amounts of pressure. The flow varies with each cycle. The power sources produce large amounts of waste heat, thereby requiring the addition of large external air blowers or fans to remove excess heat from the power source to prevent over-heating problems. Directional control of the fluid supply requires the use of a directional control valve, typically of a solenoid-type, which are susceptible to failure.
It is an object of this invention to provide an hydraulic power system for operating an hydraulic actuator mechanism which reduces or eliminates the above referenced problems, by providing a system which is compact, has excellent heat transfer characteristics such that no external air cooling devices are required, can be stacked or connected in parallel to selectively increase horsepower, is controlled electronically to adjust the speed of the motor to provide the flow and pressure which matches the load, which provides for redundant power sources in the event a single power source fails, and which is usable in cold climates without the need for preheating of the fluid. It is a further object to provide such a system which is low cost yet provides multiple speed, flow, load and horsepower options, which is relatively small in size relative to its output, and is very quiet. It is a further object to provide such a system which does not require an electrical solenoid valve as a selector valve for reversing flow direction, such that the rotation of the motor itself determines the flow path to the actuator mechanism. These and other objects will be apparent from review of the following disclosure.
The invention is in a most general sense an hydraulic power system comprising a bi-directional or reversible electric motor pump for pressurizing and inducing flow in a liquid to operate an actuator mechanism, such as a piston within a cylinder, hydraulic motor or the like, where the motor pump is immersed in the liquid within the storage and return reservoir, the liquid acting as a heat transfer means to maintain the motor within operational parameters without the need for extraneous cooling mechanisms, blowers or the like. In a further general sense, the invention is an hydraulic power system where the flow direction of the hydraulic power system is controlled by the direction of rotation of the motor and pump without the need for an electrically operated directional control valve. In a further general sense, the invention is an hydraulic power system where multiple individual power systems may fluidly connected in parallel in order to control or vary the horsepower produced by the total system dependent on need and to provide redundancy to the system in the event of the failure of an individual power system.
The invention comprises in a more detailed sense a reservoir, such as a tank or drum, which retains a liquid suitable for hydraulic applications, such as an oil or known hydraulic fluid. The liquid is pressurized and flow is induced by an electrically powered reversible motor and pump combination, and the motor and pump are immersed in the liquid within the reservoir, which is sealed but provided with a pair of delivery/return ports for flow of hydraulic fluid in either direction. A flow directional control means comprising a pair of suction conduits and one-way check valves is provided in fluid communication with the liquid in the reservoir and with the pump, such that rotation of the pump in a first direction will draw fluid through one of said suction conduits to deliver the fluid out of the reservoir through one of said delivery/return conduits to an actuator mechanism, with fluid returning back into the reservoir through the other of said delivery/return conduits, and vice-versa when the rotation of the pump is in the opposite direction. The rotation speed of the motor and pump combination is electronically controlled. Relief valves are provided to prevent overload of the system, and a differential flow control valve is provided to balance the flow as the actuator mechanism moves under the induced pressure from the hydraulic fluid.
Multiple motor and pump combinations may be immersed in a single reservoir and connected in parallel, or multiple reservoirs with motor and pump combinations may be connected in parallel, with all motor and pumps controlled electronically, such as through a microprocessor, such that the overall output power of the multiple systems can be readily varied as required by load or demand.